During the past years, computing devices such as computers, mobile phones, game consoles, personal digital assistants, etc., have evolved so much that they are able to receive a large variety of content. Most of the content, e.g., media files, arrives at the computing device through a communication network. The content may be stored in caches distributed at different locations in the communication network for improvising the content delivery.
Traditionally, a cache was located upstream a core network of the communication network, usually outside the network. More recently, to improve the content access of the end user, caches are located inside the communication network, sometimes downstream the core network. Thus, when retrieving the content from a cache located inside the communication network, the data stream provided to a user terminal might not pass through interfaces upstream of the cache. In this case, the data stream starts at the cache and goes through a downstream interface to the client, by-passing the core network. This process is advantageous as it may save internet transit and transmission costs for all interfaces above the cache.
However, the following problem is generated by this approach. For example, in the Third Generation Partnership Project (3GPP) mobile networks a Packet Data Protocol (PDP) Context is set up between the core network and the user terminal for data transmission. However, an operator requirement to the 3GPP standard is that a timer should be present in the core network and this timer is configured to time out upon inactivity, i.e., if no data is transmitted in the PDP context and to release the PDP context.
Thus, if no data is sent through a connection to the user terminal, the connection may time out and the connection may be taken down. One example is the above noted PDP context in a Wideband Code Division Multiple Access (WCDMA) network. Another example is the Enhanced Packet Service (EPS) bearers in a Long Term Evolution (LTE) network. Other networks suffer from the same problem but for simplicity, the following discussion refers only to WCDMA and LTE networks.
If no data is passing through the core network in WCDMA or LTE, the inactivity timers will trigger the PDP context/EPS bearer to be released. When the content is retrieved by the user terminal from a cache located below the core network, e.g., the Radio Network Subsystem (RNS) in WCDMA or eNB in LTE, that content will not pass through the core network. If no data passes through the core network within a configured time limit, the PDP context/EPS bearer are released. The probability that the user terminal sends/receives other traffic that could pass through the core network decreases with increased size of the objects that are retrieved from the cache.
When the core network inactivity timer expires, a Radio Access Network (RAN) in the WCDMA is ordered to release the PDP context. According to the 3GPP standard, there is no possibility for the RAN to refuse a PDP context release. If the core network is unaware of the cache in RAN, which is the most probable case, there are no existing means to stop the core network from releasing the PDP context/EPS bearer.
One approach to solve this problem is to send keep alive signals from an application running on the user terminal. However, for this case, the user terminal is unaware of the fact that it is accessing a cache downstream the core network instead of an internet server upstream of the core network. Thus, the user terminal is unaware of the need to send keep alive signals during a session in which the content is received from a cache downstream of the core network.
Further exacerbating this problem is the fact that characteristics of inactivity timers in the core networks vary among operators, for example, from 5 to 15 minutes. This means that an ongoing video session of more than 5 to 15 minutes, played from the cache to the user terminal, would be interrupted when the PDP context is released. Depending on the client application, the video would either be restarted from the beginning or not at all. In the best case, there will be an interruption in the video stream for several seconds, while the PDP context is re-established.
Alternatively, the connection between the user terminal and the cache may also be dropped and the content manually restarted from the beginning. This is user terminal dependent. However, interrupting the content transmission from the cache to the user terminal is annoying for the user, especially if the content is a video file.
Accordingly, it would be desirable to provide devices, systems and methods that avoid the afore-described problems and drawbacks.